Objective: For students to observe and collect actual data, with uncertainties, of radioactive decay at work, and to gain an understanding of how it is used in radiometric dating.

Materials needed:

Cesium-137/Barium-137m MINIGENERATOR

plastic dropper bottle with 0.04M hydrochloric acid-saline solution

glass petri dish

Geiger counter

video camera with stand

Demonstration:

After hooking the video camera into a projector in the classroom, setup the video camera to point at the Geiger counter readout. Place petri dish near the Geiger counter. Take the caps off of the MINIGENERATOR and the plastic bottle. Push the plastic bottle into the top end of the MINIGENERATOR until it snaps into place. Squeeze the plastic bottle such that the acid-saline solution runs through the MINIGENERATOR and into the petri dish, 2-3 drops worth. Hold the Geiger counter sensor over the dish and have the students record the measurements they see every 10 to 30 seconds, for about 10 minutes. From their observations the students can then calculate the half-life of the Cs137. It is also useful to have the students record the data onto both standard and semi-log graph paper.

Illustrated is the full setup of this demonstration, and the projection of the setup on the screen using the video camera.